Method of and apparatus for compressing gas

ABSTRACT

AN ARRANGEMENT FOR COMPRESSING GASES OF RELATIVELY LOW MOLECULAR WEIGHT CONSISTS IN CREATING A GAS-LIQUID EMULSION FROM THE GAS, THE EMULSION BEING FORMED BY INJECTION OF THE GAS INTO A LIQUID WHICH HAS PREVIOUSLY BEEN BROUGHT UP TO SPEED; THE EMULSION IS THEN SLOWED DOWN IN A DIFFUSER THEREBY UNDERGOING COMPRESSION, AND THE TWO PHASES-GAS AND LIQUID-ARE THEN SEPARATED. THE COMPRESSED GAS IS THEN PASSED TO ITS POINT OF UTILIZATION AND THE LIQUID IS THEN PUT THROUGH A PUMP WHERE IT REGAINS THE ENERGY WHICH IT HAD GIVEN UP TO THE GAS AND IS THEN RE-CYCLED WITH FRESH GAS TO BE EMULSIFIED AND COMPRESSED.

Feb. 2,, 1971 R. B IDARD 3,559,375

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United States Patent Int. Cl. Bind 19/00 US. C]. 55-45 12 Claims ABSTRACT OF THE DISCLOSURE An arrangement for compressing gases of relatively low molecular weight consists in creating a gas-liquid emulsion from the gas, the emulsion being formed by injection of the gas into a liquid which has previously been brought up to speed; the emulsion is then slowed down in a diffuser thereby undergoing compression, and the two phasesgas and liquid--are then separated. The compressed gas is then passed to its point of utilization and the liquid is then put through a pump where it regains the energy which it had given up to the gas and is then re-cycled with fresh gas to be emulsified and compressed.

This invention relates to an improved method of and apparatus for compressing gases of relatively low molecular weight.

Turbo-compressors, whether centrifugal or axial, are not very suitable for compression of gases of low molecular mass, by reason of the large number of stages which become necessary as soon as the desired compression ratio becomes high.

Although volumetric type compressors (piston, blade or lobe types, or any other model), lack this drawback, they .have others just as serious: as a matter of fact, aside from the difficulties of lubrication, they are generally suitable only for relatively limited volume outputs.

Therefore, when it is a question of compressing large outputs of light gases, there is no fully satisfactory solution.

The present invention, relates to devices meeting this need; it goes without saying, however, that they are equally capable of compressing heavy gases if the need arises.

The sought-for result is obtained with the aid of a process utilizing a fluid flow in two phases, namely a liquid phase and a gaseous phase in the form of bubbles intimately mixed in. With this in mind, in order to compress the gas, the gas is emulsified with a liquid having substantially the same pressure, but previously brought to speed; this emulsion is then slowed down in a diffuser where it is compressed, and the two phases are then separated in a separator.

The gas thus compressed flows toward the place of utilization, and the liquid (which is at this moment at a pressure substantially equal to that of the compressed gas) is sent to a pump where it again receives the energy which it gave up to the gas.

This pump can be actuated by an electric motor, a steam turbine or, generally speaking, any machine producing mechanical energy.

The liquid then passes into an expansion channel where it is returned to substantially the initial pressure of the gas to be compressed, and finally back to the emulsifier and so on.

In a variation, the emulsion is also subjected to a pressure gradient, obtained in a centrifugal force field, and compressed in this force field.

In every case, the heat produced by the compression, is removed by a cooler. This cooler can be placed either in the main circuit of the liquid or in a directed liquid flow taken from the main circuit at a suitable point on this circuit, and reintroduced at another point of lower pressure, the difference of these two pressures being provided to compensate for the losses of head of the said cooler.

The pump, which, of course, has fixed vanes or mobile vanes, is preferably a special model, which does not substantially raise the pressure of the fluid, but on the contrary increases its kinetic energy, which it is possible to do with very good efliciency. As a variation, one provides for combining this machine with all or part of the expansion nozzle which follows, thus arranging it so that the pressure will diminish in passage into the said machine, without thereby having this machine cease to absorb the mechanical energy: in this case the expansion in the following nozzle will be diminished or even cancelled out.

The liquid circulating in closed circuit can be of any kind, provided it is physically and chemically compatible with the gas to be compressed. but, in order to reduce the variation in speed of this liquid, one can be led to use a rather heavy liquid, which turns attention to liquid metals, although ordinary water can also be suitable.

The attached drawing shows, by way of example, two modes of embodiment of the current invention.

FIG. \1 is a schematic view in section, of a first mode of embodiment.

FIG. 2 is a partial view, in axial section, of an axialtype pump capable of being used.

FIG. 3 is an exploded view of the grids of fixed and mobile vanes.

FIG. 4 is a diagram of the speeds of the fluid in the vanes.

FIG. 5 is a view in axial half-section of a second mode i of embodiment of the invention.

FIG. 6 shows a variation.

The same reference numbers have been used in the various figures to designate corresponding components.

In the mode of embodiment shown in FIG. 1, the emulsifier is constituted by a plurality of tubes 1 pierced with holes 1a, fed in parallel by an intake duct 2 for the gas to be compressed, which is thus introduced into the liquid previously brought to speed; at the outlet from the emulsifier 1, the emulsified fluid slows down as it is compressed in a diffusing channel 17 with evolute section; it then passes through a separator 3 where the compressed gas bubbles are evacuated from the open surface 4, represented in dotted lines, and duct 5, perpendicular to the plane of the figure.

There is represented in the drawing, a centrifugal separator in which the fluid traverses about of a turn, but it is understood that any other type of separator, as well as any other type of emulsifier than the one represented could be utilized.

The pump 6 makes it possible to restore to the liquid, thanks to the motor machine 7 which drives it, the energy consumed to compress the gas. A part of the liquid output can circulate through the cooler 9 thanks to a tap pipe 8 and return pipe 10. However, as stated above, the heat exchange surfaces of this cooler could be placed directly in the main flow.

The liquid compressed by pump 6, is accelerated, as it expands in nozzle 11, before returning to emulsifier 1.

As a variation, the nozzle 11 can be reduced or even eliminated, to the extent that an acceleration is already produced in machine 6, as will be explained below.

For this machine 6 one can use a conventional pump, but, since in any case the liquid, after separation of the gas, has to transform its pressure (which at this moment is the same as that of the compressed gas) into speed, before being emulsified, it is preferred to use a machine in which mechanical energy is transformed directly, in situ, into kinetic energy of the fluid, and not into pressure: in this case the fluid emerges from this machine having the same pressure as when it entered, but a higher speed.

As a variation, one can also expand the fluid to the lowest pressure, that of entry into the emulsifier, still in the same machine, the output speed then being raised by so much: it is then a case of an energy consuming machine, such as a pump, but one in which the pressure diminishes as in a turbine. Such a pump can have very high efliciency because it is known that machines in which a fluid expands have fewer losses than those in which a fluid is compressed. It will be understood that in such a machine, the fluid expands from a pressure P to a pressure P but also receives energy, and is thereby animated, at the outlet, with a speed higher than that which it would have had by expanding, purely and simply, in a nozzle fixed between these two same two pressures. Such a nozzle can advantageously replace the conventional pump 6 in FIG. 1 and even all or part of the expansion nozzle 11.

Thus one can use, for this purpose, an axial pump such as the one represented schematically in FIGS. 2 and 3, comprising a rotor 12, a stator 13, a mobile vanegrid 14 and a fixed vane grid 15, the axis of the machine being represented at 16.

In these figures and in the diagram in FIG. 4, V1 represents the absolute entry speed on the mobile grid 14, and V3 the exit speed of the fixed grid 15: these speeds are assumed to be substantially parallel to the axis. If U is the peripheral speed of entrainment of the mobile wheel, the vectorial composition VlU=W1 gives us the direction and the magnitude of the relative speed of entry on the mobile grid 14, or W1. This mobile grid deflects the flow according to W2 in the relative reference system, as it provokes a tangential deflection in the direction of the speed of entrainment U, hence absorbs work, but likewise increases this speed in value (expansion), thanks to a substantial increase in the axial component. This is obtained by reducing the axial section of passage, in the direction of flow, thanks to a suitable conicity of the stream, as shown in FIG. 2.

The fluid then arrives on the fixed vane system which follows 15 with the value V2 according to the vectorial composition V2=W2+U.

This grid 15 rectifies the flow in the opposite direction to the foregoing, according to V3, while increasing this speed in value, again thanks to a substantial increase in the axial speed, obtained with the aid of a suitable conicity 0 of the stream represented in FIG. 2.

This arrangement is only an example, because it is possible, without departing from the scope of the invention, to combine several stages like the one represented, in series, or to invert the positions of the fixed and mobile grids, one on either side, which can share the necessary tangential deflection.

The two cases, the one in which work is done at substantially constant pressure during the passage through the machine, and the one in which expansion takes place in total, do not differ fundamentally, and they both arise from the arrangement according to FIGS. 2, 3 and 4 because, in both cases, the exit speed is greater than the entry speed, and these two cases differ only in the degree of increase in this speed.

Moreover in FIG. 2 an axial type or helix pump is represented but the same result can be achieved in the same way, that is to say by increasing the output component of the speed, with a centrifugal, or even centripetal type pump, without departing from the scope of the invention.

The device as described above can be applied in rather diverse geometries.

In FIG. 5 there is represented a geometry of the toric type in which the diverse constituent elements of the circuit are disposed in a ring around an axis 16 which is likewise that of the motive turbo-machine.

In this figure one again finds certain components from the preceding figures, with the same reference numbers, but neither the cooler nor its connections with the main circuit have been included.

The emulsifier 1 is annular in shape, a body of revolution around axis 16, and is fed by an annular torus 18 which receives feed duct 2 for the gas to be compressed; the emulsifier is also, by way of example, represented by a plurality of tubes pierced with holes, placed across the flow.

One then finds the annular space 17 where compression of the emulsion takes place by reduction of the speed; this speed reduction is aided by the centrifugal character of the flow, because constantly increasing sections are offered to it.

One then finds separator 3 which was represented in the form of a toric vortex, with a free surface 4 likewise in the form of a torus.

The ducts 5 evacuate the compresed gas toward an exhaust collection torus 19, and an exhaust duct 20, and the liquid, free of gas bubbles, is returned through an annular space 21 where a first speed-up takes place, toward an acceleration zone 22; this zone is represented as fitted with a grid of fixed vanes in an annular shape, capable of conferring on the fluid, aside from an accrued outflow component, a certain tangential deflection if this is deemed necessary.

The fluid then passes through rotor 12 of the pump, provided with a mobile grid 14, then a fixed grid 15, which is also an accelerator, and finally, the emulsifier 1 again, and so on.

In this figure, the pump rotor has been placed in the region of fiow situated closest to the axis of symmetry of the device. It goes without saying that this machine can be placed in some other place in the flow, further away from the axis: in this case, the rotor of the machine can assume a centripetal form.

Furthermore, from the point of view of this motive machine, it is of no consequence whether or not one reverses the movements of the fixed and mobile parts; one can therefore just as well have the parts, listed as fixed in FIG. 3 be mobile and, on the contrary, make the parts listed as rotary, fixed. In this case there will be a field of centrifugal forces in the parts which are now rotary in the main circuit, a force field which can be utilized to compress the emulsion on the one hand, and separate the bubbles of gas from the liquid on the other hand. In this case, it is advantageous to form the emulsion at the point of minimum pressure, that is to say in the region closest to the axis of rotation. The fixed vanes, for their part, can be placed anywhere in the liquid return circuit toward this emulsifier.

One thus ends up with an arrangement like the one shown in FIG. 6. In this figure, only the sectional rotary parts have been hatched: they turn with shaft 16. One finds here, with the same reference numbers, certain components from both of the preceding figures. The emulsifier 1, here again illustrated with tubes pierced with holes, is assumed to be rotary; it is fed by the intake torus 18, likewise rotary, and the fixed orifice 2. In the rotary annular space 17, fitted with vanes that are preferably radial, compression is obtained by centrifugal effect and deceleration.

The gas is separated in a rotary separator 3 where a free surface 4 of cylindro-conical form is produced. Ducts 5 evacuate this compressed gas toward a collection torus 23, a fixed collector 19, and a fixed duct 20. The liquid, freed of its bubbles, is led back toward the axis by an annular space 21 where a certain speed-up is produced. This space is preferably provided with a vane system, preferably with radial vanes. Then the liquid encounters a fixed vane system 24 where it is further accelerated as its pressure diminishes.

One will understand that this fixed vane system is designed to impart to the fixed parts a couple compensating for that which has to be expended on shaft 16 to rotate the rotor assembly. It goes without saying that this vane system could be at some other point on the water return circuit, for example, further upstream and further from the axis, without departing from the invention.

Then the liquid again encounters a mobile vane system 25 where it finishes accelerating, while acquiring a suitable tangential speed, then once more the rotary emulsifier 1 and so forth.

The speed diagram of vane systems 24 and 25 has not been represented, because it is obtained in a manner analogous to that described in regard to vane systems 14 and 15 in FIG. 2; that is to say with observation on the one hand of the suitably oriented tangential deflections so that there will be consumption of energy on the shaft (couple absorbed) and on the other hand, observing a suitable increase in the outflow component of the speed of the liquid.

Naturally, it would be possible to make the emulsifier tubes fixed without departing from the scope of the present invention, but at the risk of increased losses of head on the liquid side (relatively greater speeds).

A device such as the one shown in FIG. 6, in which all the relative speeds with respect to the walls can be very low, can have very high efiiciency.

I claim:

1. The method of compressing gases of relatively low molecular weight which comprises the steps of injecting the gas to be compressed into a stream of liquid flowing at an elevated velocity thereby to establish gas-liquid emulsion, thereafter reducing the velocity of said emulsion to increase the pressure thereof, and thereafter separating said emulsion into its gaseous and liquid components.

2. The method of compressing low molecular weight gases as defined in claim 1 and which includes the further steps of restoring kinetic energy to said separated out liquid by increasing its velocity to its initial value, and recirculating said liquid to the point at which fresh uncompressed gas is introduced into it.

3. The method of compressing low molecular weight gases as defined in claim 1 and which includes the further step of cooling said liquid following separation of the compressed gas therefrom.

4. Apparatus for compressing gases of relatively low molecular weight comprising means establishing a closed path for circulation of a stream of liquid, means injecting the low molecular weight gas into said liquid stream at a point along said path where said liquid flows at an elevated velocity thereby to establish a gas-liquid emulsion, a diffuser located in said path downstream from said gas injection means and which functions to slow down the speed of the emulsion and correspondingly increase its pressure, a separator located in said path downstream from said ditfusor for separating the emulsion into its compressed gaseous and liquid components, and pump means located in said path downstream from said separa tor for restoring kinetic energy to said liquid prior to presensing it to said gas injection means for recycling.

5. Apparatus as defined in claim 4 for compressing low molecular weight gases wherein said pump means includes an expansion channel at the outlet side thereof in which the liquid is accelerated before being re-emulsified.

6. Apparatus as defined in claim 4 for compressing low molecular weight gases wherein said pump means functions to increase the kinetic energy of said liquid without substantially varying its pressure.

7. Apparatus as defined in claim 4 for compressing low molecular weight gases wherein said pump means in increasing the kinetic energy of said liquid also diminishes its pressure to the entry pressure of said gas injection means.

8. Apparatus as defined in claim 4 for compressing low molecular weight gases wherein said closed path, gas injection means, dilfusor and separator components are arranged about the axis of said pump means in a symmetry of revolution whereby said components assume an annular or torus configuration.

9. Apparatus as defined in claim 8 for compressing low molecular weight gases wherein said separator has the configuration of a torus with a circular meridian section and the free surface of the liquid also assumes this same configuration.

10. Apparatus as defined in claim 8 wherein said diffusor in which compression of the emulsion takes place is annular and rotary and is fitted with a vane system which is preferably radial.

11. Apparatus as defined in claim 4 for compressing low molecular weight gases wherein said separator has a cylindrical configuration and the free surface assumes a cylindro-conical configuration.

12. Apparatus as defined in claim 4 for compressing low molecular weight gases wherein said pump means is constituted by an axial flow pump with cooperating systems of fixed and rotary vane grids.

References Cited UNITED STATES PATENTS 441,252 11/1890 Nezeraux 2611 18X 2,521,215 9/1950 Haddeland et al. 261-36 SAMIH N. ZAHARNA, Primary Examiner R. W. BURKS, Assistant Examiner US. Cl. X.R. -48 

